Pagine

What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

The
Marantz Model 1070 stereo console amplifier was designed by American engineers,
but is manufactured under their control in Japan. With a total power output
approaching 100 watts RMS, it is compact in comparison with many competitive
amplifiers, yet has a wide range of facilities.

The
amplifier is fully screened, with a metal housing finished in imitation wood
veneer, and the brushed aluminium front panel is protected by a removable clear
plastic cover. The main controls are mounted on a recessed black anodized panel
with a clear perspex protective cover over the lettering and control
calibrations. This panel is not back illuminated and therefore it is essential
that the panel is placed in a good light. The controls on the front panel are a
large selector knob for phono, tuner, auxiliary, tape 1 and tape 2. Next comes
the tape monitor switch which can select either of two tape machines. In the
centre are three slider-type tone controls for bass, mid-range and treble. To
the right of these controls is the mode selector switch for left, right,
Stereo, stereo reverse, and mono L R, and finally the rotary volume control.
Below the main controls are the following: sockets for stereo microphone and
headphones, push-buttons for low filter, high filter, loudness, main speakers,
remote or ambience speakers, and power on-off. In the centre is the balance
control.

There
are four fuses to protect the amplifier and loudspeakers but to gain access to
these it is neces.snry to remove the outer top cover. The well-designed rigid
chassis carries a heavy Marantz Model 1070 stereo amplifier power transformer,
fully screened. Separate printed circuit boards are used for the stabilized
power supply, the input pre-amplifiers and tone control circuits. The fully
complementary output stages are mounted on heavy heat sinks together with the
penultimate driver stages. Whilst conventional soldering is used on switches,
plugs etc, inter-panel wiring makes use of wrapped joints, a technique claimed
to have a lower contact resistance than soldered joints.

On the
rear panel are eight spring-loaded terminals for the main and remote pairs of
loudspeakers, and below these are a 200W unswitched AC mains flat-contact
American socket and a similar switched 100W one. Normally the pre-amplifier is
directly connected to the power amplifier but, with the gradual use of graphic
equalizers, for example, it is desirable to separate the pre-amplifier from the
power amplifier. In the case of the Marantz 1070 this is achieved by having
left and right 'pre-out' and `main-in' phono sockets on the rear panel. These
automatically bridge together but, when a phono plug is inserted, the internal
connection is interrupted and any external unit can be connected between the
two parts of the amplifier. There are input and output phono sockets for two
separate tape recorders, duplicated with DIN sockets. Finally there are three
pairs of phono sockets for phono, tuner and auxiliary. A 168cm (66-inch)
three-core mains cable is permanently fixed to the amplifier.

Specifications

Gain-Phono (low
level) to pre-amp: 55 dB

Phono to recording
output: 40 dB

High level to
pre-amp output: 15 dB

Input Impedance

Low
level input Phono, Microphone: 47 kΩ

High
level input: >50 kΩ

Input sensitivity

Phono (low): 1,8 mV to equal 1 volt output at pre-amp out

Frequency
Response: 20 - 20,000 Hz; ±1 dB at rated power output

Intermodulation
Distortion: Less than 0,3% at rated
power output (SMPTE)

Damping
Factor (20-20,000 Hz): Greater than 20
into 8Ω load

Total Noise

From
magnetic phono input to power amp output:
Less than 1,5 μV equivalent
input at rated output into 8Ω

Volume
Tracking: Within 3 dB

Rated Power Output
(continuous average per channel, all channels driven)

Power to the entire
stereo system can be controlled from either the front panel power switch or the
turntable's power switch. A current sensing relay connected to the turntable AC
power outlets is controlled by the turntable power switch. The relay, in turn
controls the AC power to the remainder of the system. Sensitivity of the
circuit is adjustable to match the current consumption of your turntable.

POWER GUARD
INDICATOR AND PROTECTION CIRCUIT

Loudspeakers are
protected from burnout by the Power Guard circuit and also by other circuits
that instantaneously disconnect the speakers in the event of the presence of DC
on the output.

Two power guard
indicators indicate when the power amplifier has reached full output. At this
point the power guard circuit begins to control amplification dynamically so
that you will not hear the harsh distorted sound of square wave clipping. In
addition your speakers are protected from burnout.

HIGH ACCURACY
TRACKING VOLUME CONTROL

The volume control,
is a step attenuator which has tracking accuracy within 1 dB throughout its
entire range. Such extremely accurate matching is achieved through
electronically controlled trimming of the resistance material deposited on
pairs of printed circuits. Tracking accuracy and quiet performance are
permanently maintained. Use does not affect performance as in ordinary volume
controls.

TURN-ON TRANSIENT
ELIMINATION CIRCUITS

Speaker outputs are
connected only after power supplies and circuits have stabilized eliminating
turn on thumps or clicks.

FIVE BAND TONE
SHAPING CONTROLS IN EITHER THE RECORD OR LISTEN CIRCUITS

Five separate
controls permit individual musical spectra shaping to satisfy personal
preference or program limitations. There is 12 dB plus or minus control at
center frequencies of 30, 150, 1.500 and 10,000 Hz. In the center (detent)
position the tone shaping circuits are not active.

ACTIVE LOUDNESS
CONTROL

Loudness controls
typically are simple, passive circuits connected to a portion of the rotation
range of the volume control. As a consequence,
loudness compensation accuracy is dependent on many variables such as speaker
efficiency, amplifier gain and differences in input level. The loudness control
is continuously variable, operates independently of the volume control, and its
contour is accurately modeled after the Fletcher Munson family of "Equal
Loudness" curves.

SPEAKER SWITCHES FOR
THREE SETS OF SPEAKERS

Three sets of
loudspeakers may be used one at a time, two together, or all three
simultaneously.

DUAL TAPE MONITOR
AND TAPE COPY SWITCHES

Two tape recorders
can record simultaneously from the program being listened to or you may record
from one to the other without interfering with the "Listen" program.

SPECIFICATIONS

POWER OUTPUT:

100 watts minimum
sine wave continuous average power output, per channel, both channels operating
into 4 ohms 20 Hz to 20 kHz, with no more than 0.05% THD

75 watts minimum
sine wave continuous average power output, per channel, both channels operating
into 8 ohms 20 Hz to 20 kHz, with no more than 0.05% THD.

OUTPUT LOAD
IMPEDANCE: 4 ohms, 8 ohms

RATED POWER
BAND: 20 Hz to 20 kHz

TOTAL HARMONIC
DISTORTION: 0.05% maximum at any power
level from 250 milliwatts to rated power per channel, 20 Hz to 20,000 Hz, both
channels operating

FREQUENCY
RESPONSE: 20 Hz to 20 kHz + 0, -0.5 dB at rated power

INTERMODULATION
DISTORTION: 0.05% maximum at any power
level from 250 milliwatts to rated power per channel both channels operating
for any combination of frequencies 20 Hz to20,000 Hz

Our original C.L.L.
system which has realized quite accurate and stable tuning condition.

We employed our
original Closed Loop Locked (C.L.L.) circuit in the 5T10 to realize extremely
accurate and stable tuning conditions at all receiving FM frequencies. With the
C.L.L. circuitry, total control is effected throughout all the stages, from the
front end to the IF and detector circuits in accordance with the crystal
controlled transmission frequency of a broadcasting station. Therefore, this
may be called the ideal tuning system offering accurate and stable tuning
conditions even if ambient conditions such as temperature fluctuate. Generally,
in the case of quartz lock and synthesizer systems, only the local ascillator
or front end is partially controlled by the P.L.L. circuitry. Therefore it is
necessary to design the IF stage and the detector stage with additional
stability. In addition, C.L.L. circuitry, like the P.L.L. ciruit, has the
capture range near the center frequency of the broadcasting station and the
required lock range to achieve a stable receiving condition. Thus, C.L.L.
circuitry always provide the perfect receiving condition thanks to powerful
feedback once the signal wave of an FM station is within the capture range and
firmly locked at the lock range. Even if the receiving frequency drifts,
feedback is applied to bring it back to follow the crystal controlled
transmission frequency, and stable reception is always obtained. In addition, the C.L.L. circuitry
incorporates a lock-retaining circuit, and no new locking is needed when power
is turned off and on once the station has been tuned in.

The
"Accutouch" System which makes the most of the C.L.L. Tuning System

The 5T10 employs the
"Accutouch" system. This system makes it possible to tune in all the
tuning circuits easily to the accurate center frequencies of broadcasting
stations. To obtain more precise tuning, an extremely narrow capture range is
set for the C.L.L. circuit of the 5T10.
It would be hard for a conventional tuning method to obtain such a precise
tuning point, since such tuning method requires observation of a center tuning
meter, which is seldom accurate enough.

The
"Accutouch" system detects the exact center tuning point utilizing a
control voltage at the C.L.L. circuit, which triggers a mechanical lock on the
tuning knob. This is a very unique system in mhich the tuning knob is
temporarily locked with a positive response at the exzct tune-in point as the
knob is gradually turned to locate an FM station. Precise tuning to a station
is possible with an incomparable accuracy compared with that of current visual
tuning systems.

IF bandwidth
Selector

In the IF stage, a
2-step bandwidth selector is provided to provide both excellent distortion and
selectivity. In the "wide"
position, 2 pairs of wide-bandwidth block filters of good group-deley
characteristics are employed to realize lower distortion, while in the
"narrow" position an additional 2 pairs of narrow-bandwidth ceramic
filters are added to offer high selectivity.

A 5-gang variable
capacitor exclusively designed for FM reception is adopted at the front end to
make the most of the excellent characteristics realized after the IF
stage. Also superb interference
rejection characteristic is obtained by improving the selectivity at each RF
amplifing circuit. The IF stage is so
designed as to be inherently low in distortion, but to make it perfect, a
quadrature wide-bandwidth detector circuit is combined with it, which not only
realizes low distortion but high S/N ratio as well.

Of course, a pilot
canceller circuit is provided in the multiplex circuit, but further the phase
characteristic of the low-pass filter is improved. A DC amp configuration is
employed at the audio output stage. All of these circuit features are specially
considered in terms of good sonic quality.

A single unit, four-channel preamplifier with unique Quadralizer for the creation of a living presence sound field in the home.

Quadraphonic stereo is the ultimate in sound realism, and with Pioneer's Model QC-800,a quadraphonic power amp (or two stereo amplifiers) and four speakers you can enjoy this sound brilliance today in your own home. This well-made, highly-advanced unit is unusually versatile. It provides a choice from any existing two-channel stereo source (tape,disc of FM), as well as discrete four-channel stereo, the most genuine and thrilling four-channel sound. And it can also be used as a conventional two-channel stereo pre-amplifier if you intend to wait until adding another pair of speakers to your existing stereo set. The QC-800 is a perfect match to Pioneer's Quadraphonic Power Amplifier (Model QM-800). And it's your most versatile introduction to the grandeur of four-channel stereo, a solid investment it the sound of the future that Pioneer has perfected today.

Your Own Acoustical Field

The exclusive Pioneer Quadralizer contained within the QC-800 creates an all-encompassing four-channel sound field in your home, giving you the same, full, life-like sansation of being in an acoustically perfect concert hall.

Choose Your Four-Channel System

The Quadralizer creates four-channel sound from any existing two-channel stereo source - either tape, disc or FM. And the QC-800 gives you a choice of three totally different four-channel effects.

Discrete Four-Channel Stereo

This is both the most authentic in terms of sound quality, and the most expensive since it requires a four-channel tape deck and special four-channel tapes. The sound is reproduced at a very high degree of fidelity, since the tape deck reproduces sound recorded on each of four separate tracks.

Matrix-Type Four-Channel Stereo

The "matrix" system of four-channel sound is one of the quadralizing effect systems in the QC-800. This systems creates a room-enveloping sound field, when signals from a two-channel program source are fed through a unique matrix circuitry contained within the preamplifier. These signals are analyzed and divided into four different signals which are then fed to four loudspeakers systems for sound reproduction. the matrix system is highly suitable for the reproduction of popular music or small combo group performances.

Phase Shift Four-Channel Stereo

The "phase shift" system of four-channel sound is another of the quadralizing effect systems in the QC-800. With this system, the conventional left and right stereophonic channels are reproduced from the two loudspeakers systems situated in front of the listener. But added to this sound is a phase-shifted 'wall of soud", or concert hall effect which emanates from the pair of loudspeakers placed behind the listener. The result is the rich depth of a live performance a slight enveloping echo effect through the two rear speakers, a thrilling musical experience. The Pioneer phase shift system is especially effective in the reproduction of classical or operatic music.

High Stability Head Amplifier

The head amplifier section of the QC-800 incorporates a 3-stage direct-coupling negative feedback circuitutilizing low-noise silicon transistors and emitter-to-emitter feedback. These features result in accurate equalizing characteristics with a wide dynamic range and stable performance.

Switch-Type Tone Controls

The tone control amplifier is a directly coupled three-stage design with a low-noise FET in its first stage. Its high, stable input impedance assures precise tone control at any setting without affecting the head amplifier. The tone controls are true switch types which regulate negative feedback. Each switching step has an effect of +/- 3 dB. Additionally, separate controls are provided for front and rear channels, permitting total control over the total tonal quality.

Versatile Inputs And Auxiliary Controls

Inputs of the QC-800 accept two turntables, two tape decks, a tuner and a choice of two other sound sources. There are separate headphone jacks for monitoring both front and rear channels. Controls include an output on/off switch, a -20 dB muting switch, high and low filters and a tape monitor switch. Versatility of the unit is practically unlimited.

Channel Level Controls

Each of the four channels is equipped with a level control, which permits total control over the sound field intensity even when different speaker types are used for front and rear listening.

Tape-To-Tape Duplicating

Because the QC-800 has a pair of tape deck inputs, tape-to-tape duplicating may be accomplished with ease. Normal two-channel tape-to-tape duplicating is also possible as if four-channel tape-to-tape duplicating.

The Pioneer Quadraphonic Power Amplifier, model QM-800 is designed to serve in a 4-channel stereo installation, together with a 4-channel preamplifier, 4 speaker systems and one or several program sources. Engineered for highest sound fidelity, it will open up a whole new world of "environmental sound."

DIRECT COUPLING OF ALL STAGES

Direct coupling of all amplifier stages greatly improves phase characteristics and permits an extremely wide frequency response down to near-DC. A load-regulated power supply unit is employed, and output power is higher than will ever be required.

LEVEL METERS FOR ALL FOUR CHANNELS

To obtain optimum sound balance in a 4-channel system, four separate level meters are provided. Moreover, the meters sensitivity can be adjusted in three stages (0, -10 and -20 dB) to permit accurate readings at all volume levels.

ADJUSTABLE lNPUT SENSITIVITY

As the power amplifier's input sensitivity can be adjusted in 6dB steps (at 0.5, 1 and 2 volts), it is easy to match with any preamplifier.

SPECIAL HIGH-RANGE SPEAKER OUTPUTS

ln addition to the four normal, full-range speaker terminals, a set of high-range speaker outputs are provided. The QM-800 can be used as an exclusive high-range amplifier in a multi-amplifier installation.

PERFECT PROTECTION OF OUTPUT STAGE TRANSISTORS AND SPEAKERS

The output transistors are protected from damage (in the case of overload or short-circuits in the speaker leads) by a dual system of relay and DC drift voltage detector circuits. The latter also guard against possible speaker damage by DC current.

UNIOUE PIONEER EXTERIOR DESIGN

The front panel is attractive as well as logically laid out. With its natural wooden cabinet, the QM-800 matches other Pioneer hi-f i components perfectly.

PROTECTOR CIRCUIT

Even if the power switch of the QM-800 is turned on, the speaker system will not operate for the first 5 to 8 seconds. This is because the QM-800 is provided with a circuit which protects transistor, speakers, etc. from possible damage due mainly to unexpected trouble.

If any of the speaker systems stops operating during a performance, or if mechanical noise (click, click, . . .) of the relays is heard continuously, a short-circuit in the speaker leads may be responsible. Turn off the power and check all speaker connections. Since the protector circuit is very sensitive, it may be activated if the power switch of the preamplifier combined with the QM-800 is turned on and off separately. It is therefore advisable to obtain AC power for the QM-800 from a switchable AC outlet of the preamplifier, as this guarantees simultaneous on-off switching of both units.

Programme sensor so that 5 stations on both FM and LW can be preprogrammed. Using the pre-set markers, and the programme buttons, any of your favourite stations can be pre-set. When the programme sensor position is selected any pre-set station on FM or LW can be picked up as you move the tuning indicator

The JBL L150. Capable of live-performance volume levels with true deep bass reproduction and high efficiency, the JBL L150 is a worthy addition to JBL's line of outstanding loudspeaker systems. JBL designed each component of this three-way floor-standing model for maximum power-flat frequency rsponse, controlled dispersion, and extended bandwidth. The newly developed low frequency driver is the product of over two years of intensive research by JBL engineers. The result of this careful engineering is clearly audible: smooth,transparent sound at any volume level, over a frequency range extending from the lowest organ tones to the limit of audibility and beyond. JBL takes as much care with the appearance as with the sound, and the elegant columnar design occupies little floor space and fits comfortably into any room.

Advantages of the Floor-Standing Design.

While bookshelf loudspeakers systems such as the JBL L150 have reached a high degree of refinement, there are a number of significant advantages to the floor-standing design of the JBL L150. Most immediately apparent to the listener is the increased bass performance. The JBL L150 will comfortably reproduce the power of an organ or bass guitar; if the bass information is in the music, the listener will hear it. To accomplish this, JBL engineers utilized both the larger enclosure volume of the floor-standing design and a passive rediator. The bass performance of the L150 is true deep bass, without the artificial boost in the mid-bass region that often substitutes for actual low frequency reproduction. The response of the L150 extends to the lowest octaves and is completely natural in sound with no hollow quality.

Another very audible advantage of the JBL L150 is the placement of the mid range and high frequency drivers at approx. ear level of the listener. Such placement aids in the perception of the sound as being "live", and also reduces the proportion of high and mid-frequency energy that is absorbed by furniture in the room. Although placing a bookshelf system on a tall stand will produce the same effect, the L150 provides much better bass performance and is also more easily integrated visually into a room.

A loudspeaker system should do more than merely reproduce the notes. It should bring the essence of the live performance into the living room. Listen to the L150 and hear what we mean.

Components

Each component od the JBL L150 loudspeaker system is designed and produced to meet the most rigorous standards in the audio industry. The loudspeaker frames are massive cast structures, machined to exacting tolerances. The magnetic assemblies are precisely manufactured oflow-reluctance iron, energized by powerful, high-grade magnets. Voice coils are hand wound and held within one turn of design specifications. Cones are designed from the best possible combination of stiffness, density, and weight.

Low Frequency

The Newly developed 300 mm (12") low frequency loudspeaker produces the powerful bass of the L150. The driver utilizes a stiff, heavy cone, coated with an exclusive damping formulation (the white material on the cone) to give it optimum mass and density. The 75 mm (3") voice coil, formed of cooper ribbon and hand wound on edge, is powered by a 4,7 kg (10,25 lb) magnetic assembly. Beacuse the voice coil is unusually large for a 300 mm driver, the L150 offers exceptional transient response and high efficiency.

The magnetic assembly is the first JBL low frequency design to incorporate a ferrite magnet. Ferrite magnets have many desirable characteristics, but these have been overshadowed in conventional designs by unacceptably high (by JBL standards) levels of second-and third-harmonic distortion. However, after two years of concentrated research, JBL engineers have developed an assembly that solves the distortion problem.

One key to the new JBL design is the Symmetrical Field Geometry (SFG). Accurate reproduction of the audio signal requires that the cone and voice coil move in or out with equal facility. This does not happen in conventional designs because the magnetic field around the voice coil gap is not symetrical; such designs generate large amounts of third-harmonic distortion. JBL's new SFG design greatly reduces this distortion by creating a symmetrical magnetic field on both sides of the gap.

JBL has also devised an innovative solution to the problem of second-harmonic distortion. As the voice coil moves in the gap in a conventional ferrite design, the electrical field produced by the coil (from the audio signal) modulates the flux in the magnetic structure. This in turn affects cone movement and generates from 3% to 5% second-harmonic distortion. JBL engineers found an ingenious solution - the Flux Stabilizer, an aluminum ring surrounding the pole piece. The Flux Stabilizer minimizes this flux modulation and thereby reduces second-harmonic distortion to 0,01% or less.

The low frequency reproduction of this driver is not only powerful, but clean, exhibiting a depth and transparency seldom encountered outside a live performance.

A 300 mm (12") passive radiator extends bass response to the lowest octaves. The passive radiator, essentially a loudspeaker cone with no magnet or voice coil but of a precise mass, takes the place of a large volume of air and allows the L150 to achieve its deep bass in an enclosure of modest size. Similar performance from a conventionally ported system would require a much larger enclosure; a completely sealed (acoustic suspension) design would be much less efficient.

Midrange

The 130 mm (5") midrange driver, housed in an isolated sub-chamber to prevent interaction with the low frequency loudspeaker, delivers clear, undistorted reproduction, even at extremely high volume levels. The combination of a stiff cone and large voice coil (22 mm, 7/8") give this driver exceptionally good transient response, crucial to accurate reproduction. The midrange driver is designed to be more efficient than the low frequency loudspeaker in order to maintain the substantial reserve dynamic range necessary to reproduce high-intensity program peaks without strain or distortion. (This reserve dynamic range is important because most music has far more energy in the midrange than in the bass or treble regions.)

High Frequency

The 25 mm (1") dome radiator produces high acoustic output with exceptional clarity and dispersion. The dome is constructed from phenolic-impregnated linen and combines stiffness with light weight; it is small enough to provide the dispersion necessary for excellent stereo imaging, yet strong enough to produce live-performance volume levels without distorting. Special clamping rings assure linear movement to further aid in distortion-free performance.

Frequenvy Dividing Network

The dividing network receives the signal from the amplifier and allocates each portion to the appropriate driver. The sophisticated network of the L150 utilizes phase-correcting and impedance-leveling circuitry so that the drivers operate through the transition frequencies in a manner approaching the theoretical ideal. All of the network components are mounted on a single large printed circuit board, which improves the already excellent reliability. The driving network of the JBL L150 does its job so well that the listener will never be aware of separate drivers - just the smooth, transparent sound.

Controls for midrange and high frequency output accomodate variations in room acoustic and personal preferences.

Enclosure

A tightly constructed, non-resonant enclosure is important to any loudspeaker system and especially importand to a robust system such as the L150. Therefore, the enclosure panels are made of dense compressed wood, superior to solid wood in its acoustic properties. For maximum strength and resistance to vibration, all panels are cut from 19 mm (3/4") stock. In addition all joints are hand fitted and heat cured. To absorb unwanted resonances, the enclosure is lined with fiberglass. The finish veneer is American black walnut, hand-rubbed to alustrous finish.

Power Capacity

The JBL L150 will produce sound at comfortable listening levels when driven by an amplifier having an output of as little as 10 watts continuous sine wave per channel. However, the L150 combines high efficiency with high power capacity; for the best possible performance, an amplifier capable of delivering up to 300 watts continuous sine wave per channel is recommended. Such an amplifier has the reserve power necessary for accurate reproduction of transients, which can reach momentary peaks equivalent to ten times the average power level.

Specifications

JBL has traditionally refrained from listing data for which no widely accepted test procedures have been establoshed. In the absence of such standards, any laboratory can legitimately produce a variety of values, depending on the conditions selected.